* {
  margin: 0;
  padding: 0;
  list-style: none;
  box-sizing: border-box;
}

html,
body {
  width: 100%;
  height: 100%;
}

.mask {
  width: 100%;
  height: 100%;
  position: fixed;
  left: 0;
  top: 0;
  background: rgba(0, 0, 0, .5);
}

.alert {
  width: 200px;
  height: 200px;
  left: 50%;
  top: 50%;
  transform: translate(50%, 50%);
  background: #fff;
}


.tab {
  width: 100%;
  height: 500px;
  display: flex;
  border: 2px solid #000;
}
.left {
  width: 100px;
  height: 100%;
  margin-right: 10px;
}
.left li {
  border: 1px solid #ccc;
  text-align: center;
  line-height: 25px;
}
.right {
  flex: 1;
  height: 100%;
  overflow-y: scroll;
}

.left .on{
  background: #06f;
  color:#fff;
}